Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Optical Spectroscopy as a Method for Skin Cancer Risk Assessment

Skin cancer is the most prevalent cancer, and its assessment remains a challenge for physicians. This study reports the application of an optical sensing method, elastic scattering spectroscopy (ESS), coupled with a classifier that was developed with machine learning, to assist in the discrimination of skin lesions that are concerning for malignancy. The method requires no special skin preparation, is non‐invasive, easy to administer with minimal training, and allows rapid lesion classification. This novel approach was tested for all common forms of skin cancer. ESS spectra from a total of 1307 lesions were analyzed in a multi‐center, non‐randomized clinical trial. The classification algorithm was developed on a 950‐lesion training dataset, and its diagnostic performance was evaluated against a 357‐lesion testing dataset that was independent of the training dataset. The observed sensitivity was 100% (14/14) for melanoma and 94% (105/112) for non‐melanoma skin cancer. The overall observed specificity was 36% (84/231). ESS has potential, as an adjunctive assessment tool, to assist physicians to differentiate between common benign and malignant skin lesions.     

Quantifizierung organischer Substanzen in Aktivkohleextrakten mit Hilfe der Gas-Chromatographie/Massenspektrometrie

Summary Use of activated carbon plays a significant role in water technology and analytical chemistry. Therefore determination of substances adsorbed on activated carbon is of special interest. As an example, granulated activated carbon (GAC) from a water treatment plant was serially extracted with different organic solvents. Quantitative determination of some selected compounds in the combined extracts was done by gas chromatography/mass spectrometry. The method of internal standard addition and calibration by response factors was used. The determined compounds (all of substituted benzene type) were extracted from the GAC in the concentration range from 0.2 mg/100 g (m-dichlorobenzene) to 5 mg/100 g (nitrobenzene). Relative standard deviation for double determination of five independent samples from the GAC filter was less than ±20%Spike experiments were performed to determine recovery efficiences. As expected, substance specific differences appeared and the recoveries were between 36% (m-dichlorobenzene) and 80% (nitrobenzene). A significant limitation for quantitative determination results from lack of available substances for calibration.     

Protonation‐Driven Membrane Insertion of a pH‐Low Insertion Peptide

The pH‐low insertion peptide (pHLIP) inserts into membranes and forms a transmembrane (TM) α‐helix in response to slight acidity, and has shown great potential for cancer diagnosis and treatment. As a lead, pHLIP is challenging to optimize because the mechanism of its pH‐dependent membrane interactions is not completely understood. Within pHLIP there are multiple D/E residues which could sense the pH change, the particular role played by each of them in the protonation‐driven insertion process is not clear. The precise location of the TM helix within the pHLIP sequence is also unknown. In this work, solid‐state NMR spectroscopy is used to address these central questions. Tracing backbone conformations revealed that the TM helix spans from A10 to D33 with a break at T19 to P20. Residue‐specific pK_a values of D31, D33, D25, and D14 were determined to be 6.5, 6.3, 6.1, and 5.8, respectively, and define the sequence of protonations which lead to insertion. Furthermore, possible intermediate states which disrupt membranes at pH 6.4 were proposed based on tryptophan fluorescence quenching and NMR data.     

Submicron streptavidin patterns for protein assembly

Micron and submicron-scale features of aldehyde functionality were fabricated in polymer films by photolithography to develop a platform for protein immobilization and assembly at a biologically relevant scale. Films containing the pH-reactive polymer poly(3,3'-diethoxypropyl methacrylate) and a photoacid generator (PAG) were patterned from 500 nm to 40 mum by exposure to 365 nm (i-line) light. Upon PAG activation and hydrolysis of acetals, aldehyde groups formed. After the films were incubated with a biotinylated aldehyde reactive probe, the X-ray photoelectron spectroscopy results were consistent with biotin being attached to the surface. The background was subsequently passivated by flood exposure and incubation with an aminooxy-terminated poly(ethylene glycol), resulting in a 98% reduction in nonspecific protein adsorption. Protein patterning and assembly was demonstrated using streptavidin, biotinylated anthrax toxin receptor-1, and the protective antigen moiety of anthrax toxin and confirmed by fluorescence microscopy and atomic force microscopy (AFM). AFM demonstrated that 500 nm protein features were achieved. Because of the abundance of biotinylated proteins, this methodology provides a platform for protein immobilization and assembly for various applications in biotechnology.     

Radiation chemistry of high energy carbon,neon and argon ions: Effects of nuclear fragmentation

Yields of Fe³⁺ from aerated and deaerated solutions of ferrous sulfate irradiated with high energy carbon or neon ions are shown to be consistent with current theoretical models of radiation chemistry, if fragmentation of the incident ion is taken into account. For argon, the observed yields are higher than predicted.     

Direct evidence for enzyme persulfide and disulfide intermediates during 4-thiouridine biosynthesis

Two proposed mechanisms for 4-thiouridine generation share key cysteine persulfide and disulfide intermediates, and indirect evidence of their existence has been previously reported; chemical trapping and mass spectrometry have now provided direct and definitive evidence of these key intermediates.     

Comparison of silicon LIII,II electron loss spectra and optical absorption

Threshold structure due to L_III,II excitation in the electron loss spectra of silicon at 100.2 ± 0.3 eV is in good agreement with optical absorption measurements of 100.1 ± 0.1 eV.     

Evidence for free radicals produced in aqueous solutions by diagnostic ultrasound

Recent theoretical calculations have shown that small gas nuclei in water exposed to microsecond ultrasonic pulses above an intensity threshold may grow into transient cavities that collapse violently, leading to the formation of .OH radicals and .H atoms. We have detected these free radicals in aqueous solutions exposed to microsecond pulsed ultrasound using spin trapping and electron spin resonance (ESR). The public health implications of our results are discussed.     

Linewidth of H chemisorbed on W(100): An infrared study

The symmetruc stretch vibration of hydrigen on W(100) at saturation is measured with high resolution by infrared spectroscopy and found to be broad (≈ 100 cm^?. This unusually large width is thought to reflect large H-H dynamical interactions.